Process for the reduction of acid losses and for the regulation of the water content in metal etching baths for wires and ribbons and device therefor



July 4, 1967 F. STIEHL 3,329,542

PROCESS FOR THE REDUCTION OF ACID LOSSES AND FOR THE REGULATION OF THE WATER CONTENT IN METAL ETCHING BATHS FOR WIRES AND RIBBONS AND DEVICE THEREFOR Filed Oct. 11, 1963 s Sheets-Sheet 1 .70 van for:

Fritz fife/II 4: :Z ltm m Mfum- July 4, 1967 F. STIEHL 3,329,542

PROCESS FOR THE REDUCTION OF ACID LOSSES AND FOR THE REGULATION OF THE WATER CONTENT IN METAL ETCHING BATHS FOR WIRES AND RIBBONS AND DEVICE THEREFOR Filed Oct. 11, 1963 I5 Sheets-Sheet 2 .70 en/or:

July 4, 1967 F. STIEHL PROCESS FOR THE REDUCTION OF ACID LOSSES AND FOR THE REGULATION OF THE WATER CONTENT IN METAL ETCHING BATHS FOR WIRES AND RIBBONS AND DEVICE THEREFOR Filed Oct. 11 1963 5 Sheets-Sheet 3 I NVEN TOR. FRITZ STIEHL United States Patent 3,329,542 PROCESS FOR THE REDUCTION OF ACID LOSSES AND FOR THE REGULATION OF THE WATER CONTENT IN METAL ETCHING BATHS FOR WIRES AND RIBBONS AND DEVICE THEREFOR Fritz Stiehl, Dusseldorf-Oberkassel, Germany, assignor t0 Kontispira Gesellschaft mit beschrankter Halt'tung fiir Eisen-U. Metallverarbcitung, .Dusseldorf-Oberkassel, Republic of Germany Filed Oct. 11, 1963, Ser. No. 315,649 2 Claims. (Cl. 156-19) The invention relates to a process and a device for the reduction of losses of etching fluid and for the simultaneous regulation of the water content, i.e., the maintenance of a given concentration of the etching fluid, in metal etching baths, such as tanks wherein metal wires and ribbons are etched and thereafter rinsed with water, and, more particularly, to the treatment of wires and ribbons which are conducted through the process in helical turns.

Etching baths for iron goods generally use sulfuric acid or hydrochloric acid. Other inorganic and certain organic acids are of lesser important. Hydrofluoric, phosphoric, oxalic and naphthalenesulfonic acid have been employed, and the instant process is applicable to all acids used for the etching of iron, especially, however, for sulfuric acid, which is a preferred embodiment.

Etching of iron goods with sulfuric acid commonly is carried out at temperatures ranging from 60 to 100 C. The concentrations are well known to the expert.

It is inevitable that at the temperatures named, a certain amount of evaporation of water occurs. Also, additional quantities of liquid are bound on iron sulfate or iron chloride forming during the process.

It therefore is necessary to add to the etching bath water as well as sulfuric acid, or hydrochloric acid, as the case may be, in order to maintain the predetermined concentrations and the level of the etching bath.

Prior art has availed itself of a pre-rinse tank for the decrease of losses in etching fluid, especially when valuable electrolytes are employed. The contents of this pre-rinse tank then have been used for the replenishment of the etching bath. It also is known to precipitate nitrous vapors, forming during etching, by means of a water pressure spray, the spray nozzles being situated in a suitable place, i.e., approximately at the center of the etching tank.

It is the object of this invention to provide a process for the reduction of losses of etching fluid which are brought about by the adherence of the fluid to the wires and ribbons when leaving the etching tank.

It is a further object of the invention to regulate the water content and concentration of the etching solution.

For the purpose, the wires or ribbons are continuously conducted through the etching and rinsing tanks in helical turns, and it is a further object of this invention to provide means whereby merely a negligible quantity of etching fiuid is carried over into the rinsing tank or tanks while a definite, but comparatively small amount of water is used for the removal of etching fluid from the wire or ribbon. The fact that merely a small amount of water is required, enables a measurement of this quantity so that this quantity corresponds to, and equalizes, just the water losses incurred in the etc-hing tank due to evaporation and binding upon the iron salt formed. Both iron chlorides and iron sulfates have water of crystallization.

The process is carried out in such a manner that the wires and ribbons are given helical turns prior to their entry into the etching tank and maintain their helical the fluid level while their upper part extends above such v level. Prior to reaching the rinsing tank the upper part of the turn of the wire or ribbon which is the last one in its direction of movement within the etching tank is sprayed with water taken from the rinsing tank following the etching tank. The rinsing water runs from the said last turn of the wire or ribbon into the etching tank and its amount is metered so that it corresponds to the water lost in the etching tank and is just suflicient to maintain the desired acid concentration and level therein as already described above.

In some cases it may be necessary or preferable that two or even more rinsing tanks are installed behind the etching tank in the direction of movement of the wire or ribbon. In such cases the helical turns of the wire or ribbon emerging from the rinsing bath and being above its liquid level are sprayed once more within the rinsing tank or tanks preceding the last one, with rinsing water taken from the immediately following rinsing tank.

Surveillance of the desired concentration is carried out in the conventional manner, e.g., by installing a pH meter in the etching tank. Preferably fresh Water is metered solely into the rinse tank or into the last rinse tank if two or more rinse tanks are installed.

It is evident that the amount of spraying water introduced intothe plant is limited since it must not dilute the etching fluid but merely replenish the losses of water incurred as explained above. Nevertheless, the invention 1 provides for an avoidance of acidulation of the rinse water within the rinsing tank or tanks behind the etching tank to a large extent, because the cleansing spray removes most, if not all, of the acid carried on the etched wires or ribbons. Simultaneously, the etched products are kept moist at all times which is of importance since, upon drying, spots and deposits form on their surfaces if they dry out while still carrying an acid film.

The invention now will be further explained with reference to the accompanying drawing, but it should be understood that this is given merely by way of illustration, not of limitation, and that numerous changes may be made in the details without departing from the spirit and the scope of the invention as hereinafter claimed.

In the drawing,

FIG. 1 is a diagrammatic plan view partly broken away showing the course of the wires or ribbons through an etching bath, one rinsing tank and two neutralization tanks.

FIG. 2 is a diagrammatic plan view corresponding to FIG. 1 with the exception that two rinsing tanks and two neutralization tanks are provided behind the etching tank.

FIG. 3 is a cross sectional view of the device showing the course of the ribbon or wires through the installation similar to FIG. 1, also the liquid level and the watersprays.

Referring now to FIG. 1 of the drawing the wire or ribbon 1 to be etched enters the etching tank 2 at one end thereof and traverses the said tank on a helical path while being supported on shafts or bars 4 and 5. These shafts or bars may be rotated thus imparting the necessary drive to the turns 3 of the Wire or ribbon. The turns 3 immerse into the etching liquid within the etching tank only with the lower part of their circumference while the upper part thereof emerges above the surface of the liquid. After passage of the etching tank 2 the wire or ribbon leaves tank 2 at its end opposite to the entrance end and runs into a rinsing tank 7, separated from the etching tank 2 by a wall 6. Prior to the entrance into the rinsing tank 7 the entered wire or ribbon 1 is rinsed, by means of spraying nozzles 13, with water taken from the rinsing tank 7. The nozzles 13 are directed to the upper not immersed part of the last turn 3 of the wire or ribbon 1, within the etching tank 2. Consequently, most of the etching liquid remains in the etching tank 2 and discharge of acid sewage is prevented. The rinsing water being sprayed upon the front and rear side of the last turn of the wire or ribbon in the region of the etching tank 2 is taken from the rinsing tank 7 through a pipe 8 by a pump 9 supplying the rinsing water through pipes 10, 11 and 12 to the spraying nozzles 13 on the front and rear side of the wire or ribbon 1. If desired, a suitable portion of the rinsing water supplied by the pump 9 may be delivered by means of pipes 14, 15 and 16 to spraying nozzles 17 on the front and rear side of the wire or ribbon. These nozzles 17 are spraying once more rinsing water upon the turn of the wire or ribbon 1 within the rinsing chamber 7. The amount of fresh water supplied through the pipe 26 into the rinsing tank 7 is metered as indicated above. The rinsing tank 7 may be followed by one or more neutralizing tanks 18, 19 traversed by the wire or ribbon 1.

The etching device shown in FIG. 2 corresponds to the device of FIG. 1, however, with the exception that two rinsing tanks 7, 7' separated by walls 6, 6' are provided behind the etching tank 2. Through a pipe 20 rinsing water is taken from the second rinsing tank 7' and delivered by a pump 9 by means of conduits 10, 11 and 12 to spraying nozzles 13 at the front and rear side of the last turn of the wire or ribbon, above the liquid level of the etching tank 1. Branch pipes 21 and 22 are delivering a portion of the rinsing water supplied by the pump 9 to spraying nozzles 23 at the rear and front side of the turn within the first rinsing tank 7. Additional branch pipes, 24, 25 may be provided for delivering a suitable portion of the rinsing water supplied by pump 9 to spraying nozzles 27 at the front and rear side of the turn within the second rinsing tank 7.

An amount of fresh water metered as indicated above may be supplied to the second rinsing tank 7' through pipe 26.

If additional rinse tanks are used, the fresh water from the common water supply always enters the last rinse tank, and spray water always is transferred from one tank to the proceeding one, starting with the last rinse water tank.

I claim as my invention:

1. In a process for etching of iron wires and ribbons in a helical path wherein said wires and ribbons are conducted through a hot acid liquid of a given concentration and then are rinsed with water in a bath, the improvements which comprise keeping said liquid at a constant concentration by conducting said wires and ribbons continuously on a helical path therethrough and through said bath, the lower portion of said turns immersing into the liquid and the upper portion of the turns emerging above the liquid level; rinsing the last turn emerging from said acid liquid with a spray of water taken from said water bath in a quantity corresponding to that lost from said acid liquid by evaporation and water of crystallization of iron salts formed during etching, and then conducting said wires and ribbons through said rinse bath, the water taken from said rinse bath being replenished by a corresponding amount of fresh water.

2. The process as defined in claim 1, wherein at least two rinse baths are provided; the last turn of said wires and ribbons emerging from each of said rinse baths being sprayed with water from the next following bath; the water in the last bath being replenished in a corresponding amount by fresh Water.

References Cited UNITED STATES PATENTS JACOB H. STEINBERG, Primary Examiner. 

1. IN A PROCESS FOR ETCHING OF IRON WIRES AND RIBBONS IN A HELICAL PATH WHEREIN SAID WIRES AND RIBBONS ARE CONDUCTED THROUGH A HOT ACID LIQUID OF A GIVEN CONCENTRATION AND THEN ARE RINSED WITH WATER IN A BATH, THE IMPROVEMENTS WHICH COMPRISES KEEPING SAID LIQUID AT A CONSTANT CONCENTRATION BY CONDUCTING SAID WIRES AND RIBBONS CONTINUOUSLY ON A HELICAL PATH THERETHROUGH AND THROUGH SAID BATH, THE LOWER PORTION OF SAID TURNS IMMERSING INTO THE LIQUID AND THE UPPER PORTION OF THE TURNS EMERGING ABOVE THE LIQUID LEVEL; RINSING THE LAST TURN EMERGING FROM SAID ACID LIQUID WITH A SPRAY OF WATER TAKEN FROM SAID WATER BATH IN A QUANTITY CORRESPONDING TO THAT LOST FROM SAID ACID LIQUID BY EVAPORATION AND WATER OF CRYSTALLIZATON OF IRON SALTS FORMED DURING ETCHING, AND THEN CONDUCTING SAID WIRES AND RIBBONS THROUGH SAID RINSE BATH, THE WATER TAKEN FROM SAID RINSE BATH BEING REPLENISHED BY A CORRESPONDING AMOUNT OF FRESH WATER. 